VIERA, Fla. — He is the Natural. Except this is no movie. The Bryce Harper Show already is something to see.

“I’ve never seen anything like this before in baseball,” veteran infielder Alex Cora told The Post of the Harper’s bazaar that is running daily this spring in the Nationals camp. “This is baseball’s version of LeBron James.”

Watch the 18-year-old Harper swing a bat and you realize Cora is not overselling this phenom story.

The explosion of power that is unleashed with each left-handed swing is shocking. Harper’s baseball hero is Mickey Mantle, and there are Mantle-esque qualities to Harper’s swing — a swing that made him the No. 1 pick last June in the amateur draft and landed him a $9.9 million contract straight out of junior college after skipping his final two years of high school.

“I’m trying to make this club,” the 6-foot-3, 225-pound Harper said this week. “Why can’t it be realistic? I’ve exceeded expectations my whole life.”

Ex-Mets manager Davey Johnson is a coach with the Nationals. He’s seen everyone from Mantle to Willie Mays to Hank Aaron to Frank Robinson to Darryl Strawberry to Barry Bonds.

As it was with Mantle, it is the bat speed and the power of Harper’s swing that gets Johnson’s full attention. He has watched Harper hit a ball 500 feet in a home-run hitting contest — at age 16.

“It’s hard not to like everything you see about him,” Johnson said as he stood near the batting cage. “From his approach, his makeup and his athleticism; he’ll dictate how soon he gets where everybody knows he’s going to go.”

The Nationals have said Harper will start the season in the minors, probably Single-A Hagerstown. Harper, a former catcher who now is playing the outfield, will not turn 19 until Oct. 16.

Not rushing to the majors is the right move at this point, though Harper is ahead of the game. Give him a little time to grow.

“He’s very mature for his age,” Johnson said. “And he’s so strong. He’s going to be fun to watch.” As for any Strawberry comparisons, Johnson said, “This kid is more analytical than Straw.”

Strawberry made the majors at age 21 in 1983 and hit 26 home runs on his way to NL Rookie of the Year honors. Mantle first came up to the Yankees in 1951 at 19. That same year Mays joined the Giants and was Rookie of the Year. Aaron made it to Milwaukee at 20 in 1954. Robinson blasted 38 home runs in 1956 to earn ROY honors when he was only 20. Bonds was 21 when he came to the Pirates in 1986.

Robinson was a visitor to Nationals camp this week and said he would have been up at 19 except for a shoulder injury that limited his throwing.

“Age doesn’t matter” Robinson said, “if you’re good enough to play in the majors.”

Harper is cocky, but in a positive way. To be a great hitter, you have to have that confidence. And Harper is quick to pay homage to baseball.

“I think every player needs to know about the history of the game,” said Harper, who studies players from past eras on MLB Network and ESPN Classic. “I love looking up stuff about Mickey Mantle, George Brett and Pete Rose. Those are my three guys that I absolutely love and want to play my game like. They went about their business every day and played as hard as they could every day.”

It’s not often an 18-year-old will bring up those three baseball icons, but Harper always is swinging for the fences. He says what’s on his mind.

Consider that at his first official Nationals press conference of the spring, he spent a good portion of that time talking about how much he loves the Yankees, singling out Robinson Cano, Derek Jeter and Alex Rodriguez.

When Harper does become a star, the Nationals had better get the most out of him while they can because when he becomes a free agent; it looks as if he will be headed directly to the Bronx. He came to Yankee Stadium for a workout in 2009 and rattled balls into the upper deck. The first thing he told scout Steve Markovich that day was, “I’m going to be a Yankee.”

Asked about being excited to play in his first spring training game, Harper answered, “I’m excited to go play the Yankees (March 5) because I want to see all those guys. I want to see Cano, Jeter and A-Rod and everybody.”

Why the Yankees?

“I love the Yankees,” he said. “I’ve always loved the Yankees ever since I was younger. They have all the studs. You just want to see how everybody goes about their business. Cano, how he warms up, Jeter, how he warms up. There are a lot of veteran guys that you can learn from and there are a lot of veteran guys I can learn from here, also.”

The Nationals’ veterans have given Harper some advice.

“Lose the eye black,” he said with a smile. Harper has. There is no fancy war paint on his face like on that SI cover from 2009 when he proclaimed he wanted to be “considered the greatest baseball player who ever lived.”

Harper also said that he wants to beat the Yankees, though the Nationals and Yankees appear never to be destined to cross paths in October.

“If I can be the Yankee breaker,” Harper noted, “and be that guy that breaks that streak of them winning, that would be great.”